Move functionality out from AudioFrame and into AudioFrameOperations.

webrtc/modules/audio_mixer/audio_mixer_impl.cc

Index: webrtc/modules/audio_mixer/audio_mixer_impl.cc
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.cc b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
index 57fae8cc0d34e28d57fd71859d6340bf3140a486..650bd6e63cf6011f264301541bed74e8fc49a274 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
@@ -108,10 +108,10 @@ int32_t MixFromList(AudioFrame* mixed_audio,
     if (use_limiter) {
       // Divide by two to avoid saturation in the mixing.
       // This is only meaningful if the limiter will be used.
-      *frame >>= 1;
+      AudioFrameOperations::ShiftDown(frame);
     }
     RTC_DCHECK_EQ(frame->num_channels_, mixed_audio->num_channels_);
-    *mixed_audio += *frame;
+    AudioFrameOperations::AddFrames(*frame, mixed_audio);
   }
   return 0;
 }
@@ -205,9 +205,9 @@ void AudioMixerImpl::Mix(int sample_rate,
     RemixFrame(number_of_channels, frame);
   }
 
-  audio_frame_for_mixing->UpdateFrame(
+  AudioFrameOperations::UpdateFrame(
       -1, time_stamp_, NULL, 0, OutputFrequency(), AudioFrame::kNormalSpeech,
-      AudioFrame::kVadPassive, number_of_channels);
+      AudioFrame::kVadPassive, number_of_channels, audio_frame_for_mixing);
 
   time_stamp_ += static_cast<uint32_t>(sample_size_);
 
@@ -219,7 +219,7 @@ void AudioMixerImpl::Mix(int sample_rate,
   if (audio_frame_for_mixing->samples_per_channel_ == 0) {
     // Nothing was mixed, set the audio samples to silence.
     audio_frame_for_mixing->samples_per_channel_ = sample_size_;
-    audio_frame_for_mixing->Mute();
+    AudioFrameOperations::Mute(audio_frame_for_mixing);
   } else {
     // Only call the limiter if we have something to mix.
     LimitMixedAudio(audio_frame_for_mixing);
@@ -330,7 +330,7 @@ bool AudioMixerImpl::LimitMixedAudio(AudioFrame* mixed_audio) const {
   //
   // Instead we double the frame (with addition since left-shifting a
   // negative value is undefined).
-  *mixed_audio += *mixed_audio;
+  AudioFrameOperations::AddFrames(*mixed_audio, mixed_audio);
 
   if (error != limiter_->kNoError) {
     LOG_F(LS_ERROR) << "Error from AudioProcessing: " << error;